Drawbench apparatus



1956 s. A. MITCHELL ETAL 3,264,857

DRAWBENCH APPARATUS 4 Sheets-Sheet 1 Filed April 10, 1964 GEORGE A. MITCHELL ATTORNEY 9, 1956 G. A. MITCHELL ETAL 3,

DRAWBENCH APPARATUS Filed April 10, 1964 4 Sheets-Sheet 3 INVENTORS GEORGE A. MITCHELL LILL ATTORNEY Aug. 9, 1966 A. MITCHELL ETAL 3,264,357

DRAWBENCH APPARATUS Filed April 10, 1964 4 Sheets-Sheet 4 RESERVOIR Fig. 3. INVENTORS GEORGE A. MITCHELL STEFAN LILL ATTORNEY United States Patent sylvania Filed Apr. 10, 1964, Ser. No. 358,728 9 Claims. (Cl. 72-281) This invention relates to dr-awbenches adapted to draw a plurality of workpieces through a corresponding number of dies. More particularly, the invention is concerned with apparatus for drawing thin-walled tubes which are subject to damage and difiiculties in stacking as a result of their being propelled forwardly at the completion of a draw due to a sudden release of kinetic energy.

As is well known to those skilled in the art, a drawbench employs, as a basic component, a circular die through which a workpiece is drawn in order to elongate it and reduce its diameter. In the drawing operation, the end of a tube or other workpiece to be drawn is passed through a die and engaged by gripper jaws carried on a draw carriage or dolly which travels on a track extending parallel to the central axis of the die on one side thereof. In the drawing operation, the draw carriage is forced along its track structure away from the die, thereby pulling the tube through the die. In the usual case, the draw carriage is driven by means of an electric motor or fluid motor, connected to the carriage through a chain or cable drive arrangement.

In order to increase the production output of a drawbench, a plurality of tubes are simultaneously drawn through a corresponding number of spaced dies during one drawing operation. It is a common occurrence in the drawing of tubes for the same to jump forwardly with considerable force as their trailing ends leave the dies, the reason being that the tubes are under substantial tension during the drawing operation, and the sudden release of such tension is accompanied by a release of energy which propels them forwardly with considerable force. The action is somewhat analogous to that occurring when one end of a stretched elastic band is released and snaps forwardly toward the other end. In the drawing of long, slender tubes of thin-walled sections with conventional drawbench apparatus, this condition is a particularly serious problem in that the forward ends of the tubes are driven against the draw carriage or other parts of the drawbench and are often buckled and rendered unsuitable for a subsequent drawing operation, or partially so. That is, when a long slender tube is driven against the draw carriage, shock waves develop along its length. If these waves are of such magnitude as to produce bends in the tube exceeding its elastic limit, permanent deformation will result, thereby producing a buckled or dog-legged condition. This condition may be severe enough to render the tube unsuitable for further processing and, in any event, it is a troublesome and heretofore persistent problem in the drawbench industry.

Various schemes have been proposed in an attempt to prevent buckling or dog-legging of newly-drawn tubes. One such proposal calls for shock absorbers on the draw carriage designed to absorb the kinetic energy of the tubes as they jump forwardly at the completion of a draw. Another proposal utilizes inclined planes or deflectors designed to direct the tubes down beneath the draw carriage where they can expand their energy by moving along a raceway beneath the draw carriage track. Neither of these systems, however, is completely successful in eliminating a dog-legged condition and raises auxiliary problems in the design of the draw carriage, tube receiving trough or other parts of the drawbench.

Another persistent and troublesome problem which has plagued the drawbench industry for years is that of uneven or tangled stacking of drawn tubes in the receiving bin beneath the bench. When a tube under tension snaps free of a drawing die, it is difficult to predict its behavior; and in the usual case the tubes often come to rest in a skewed and uneven condition in the receiving bin of the bench. The most troublesome aspect of random positioning of the tubes in the receiving bin is misalignment of their ends. In most drawing operations, a number of the tubes are stacked in the receiving bin and are thereafter elevated by means of an overhead crane to the loading trough of a drawbench for further processing. This condition of nonalignment of tube ends makes it difficult for the operator to load the tubes onto the drawbench mandrels during a succeeding drawing operation and, in any event, slows down the production rate of the drawbench.

As one object, the present invention seeks to provide new and improved means in a drawbench for absorbing the kinetic energy of newly-drawn tubes in a manner to prevent damage to their forward ends as a result of being propelled against the draw carriage or other parts of the drawbench at the completion of a drawing operation.

Another object of the invention is to provide apparatus in a drawbench for facilitating even and uniform stacking of drawn tubes in a receiving bin beneath the bench with the forward ends of the tubes aligned, or at least substantially aligned.

Still another object of the invention is to provide apparatus of the type described particularly adapt-able for use in a multiple draw tube drawbench.

In the past, proposals have been made for preventing dog-legging by providing a pair of pinch rolls which are separated when the draw carriage is adjacent the die preparatory to a drawing operation, but which are forced together into frictional engagement with the workpiece during the drawing operation when the draw carriage moves away from the die. In the case of a multiple draw, this proposal calls for unitary pinch rolls on opposite sides of all workpieces, the inherent inertia or frictional resistance of the unitary rolls being employed to dissipate the kinetic energy of the workpieces. This system is satisfactory for single drawbenches, and serves also to dissipate the kinetic energy of drawn tubes in a multiple drawing operation; however it has one somewhat serious limitation when applied tomultiple drawbenches. This is its inability to align the trailing ends of the tubes at the completion of the drawing openation, which inability is due primarily to the fact that there are only two unitary rolls on opposite sides of all tubes. Since the tubes do not leave their associated dies simultaneously, this means that each tube cannot be moved forwardly through the rolls independently of the others, and all but the last are retarded by tubes still in tension.

In accordance with the present invention, the problem of aligning tube ends at the completion of a multiple draw is eliminated by providing pairs of pinch rolls individual to each tube in a multiple drawing operation whereby the action of each tube is independent of the others. Surprisingly enough, this achieves the new and unexpected result of align-ing the tube ends, which result has not .been satisfactorily achieved with any device heretofore known. Preferably, the pinch rolls are utilized in combination with a tilting table beneath the tubes. The table is positioned in a horizontal plane until all tubes come to rest following a multiple drawing operation, and is thereafter tilted downwardly following a drawing operation to discharge the tubes into a receiving bin. This insures that all tubes .roll into the receiving bin in more or less parallel relationship and eliminates a condition wherein the forward ends of the tubes drop into the bin before their trailing ends and create a tangled condition.

While the inherent inertia of freely-rotatable rolls is suflicient to dissipate the immediate surge of energy of a drawn tube as it snaps through its die, nevertheless the rolls and tube will thereafter have a certain velocity. Therefore, in order to completely stop the tube while it is gripped between the rolls, it is desirable to apply a retarding force to the rolls. -In the case of relatively heavy, thick-walled tubes, this retarding force may be applied continually during the entire drawing operation. On the other hand, when thin-walled tubing is being drawn, the retarding force is preferably not applied until the tube snaps free of tits die. That is, since it is desirable to employ the highest possible drawing force without exceeding the elastic limit of the tube, the application of any braking effort to the rolls during a drawing operation on thin-walled tubing could cause breakage of the tubes.

Therefore, in accordance with another aspect of the invention, releasable braking means are provided for each independent set of rolls, together with apparatus for actuating the braking means to retard rotation of the rolls when the trailing end of the tube gripped by the rolls leaves its associated die. Preferably, the braking means is of the electromagnetic type since, among other reasons, the speed of the tube is very high, and mechanical brakes cannot be actuated quickly enough after the tube leaves the die. Furthermore, the electromagnetic braking arrangement provides a more even and uniform braking effort in slowing down the tubes and dissipating their kinetic energies.

In order to sense passage of the trailing end of the tube through the die, various arrangements may be employed; however the system preferably employs photocells and light beams which are interrupted by the tubes while they are in the dies, but which shine upon the photocells after the trailing end of each tube leaves its associated die. As will be understood, one such photocell and light beam is necessary for each tube drawn in order that the sets of pinch rolls individual to each tube can be independently controlled.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification, and in which:

FIGURE 1 is a schematic side view of one embodiment of the invention;

FIG. 2 is a partially broken-away top view of the drawbench arrangement shown in FIG. 1 taken substantially along line 11-11 of FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along line IIIIII of FIG. 1 and showing in elevation the pinch roll assemblies of the invention;

FIG. 4 is a cross-sectional view taken along line IV--IV of FIG. 2;

FIG. 5 is a cross-sectional view of one of the pinch roll assemblies utilized in accordance with the invention;

FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5 showing the arrangement of the electromagnetic braking means of the invention;

FIG. 7 is an illustration of the actuating mechanism for the tiltable workpiece supporting table shown in FIG. 3;

FIG. 8 is a schematic circuit diagram of the control system for the electromagnetic braking apparatus of the invention;

FIG. 9 is a top view of a roll assembly usable in accordance with the present invention and incorporating means for applying a continual braking force to the rolls;

FIG. 10 is a cross-sectional view taken along line X-X of FIG. 9;

FIG. 11 is a bottom view of an alternative arrangement of inertia rolls incorporating individual wear adjustment means for each roll;

FIG. 12 is a cross-sectional view taken substantially along line XII-XII of FIG. 11; and

FIG. 13 is a schematic diagram of an arrangement for insuring centering of the upper and lower rolls of the invention with respect to the center line of draw.

Referring now to the drawings, and particularly to FIGS. 1-4, three tubes 10, 12 and 14 are shown being drawn simultaneously through dies 16, 18 and 20, respectively, arranged in side-by-side relationship in a die plate 22. In accordance with usual practice, the tubes 1014 are initially loaded onto elongated mandrels, not shown, disposed to the right of the die plate 22 as viewed in FIGS. 1 and 2. Thereafter, reduced diameter ends of the tubes are inserted through the dies 16-20 and engaged by gripper jaw assemblies, hereinafter described, carried on a draw carriage 26.

As shown, the draw carriage 26 is provided with bottom rollers 28 and side rollers 30 adapted to engage the horizontal and vertical portions of a pair of L-shaped tracks 32 and 34, possibly best shown in FIGS. 3 and 4, which extend parallel to the axes of dies 1620 on the sides thereof opposite the aforesaid mandrels. The tracks 32 and 34 are carried on a plurality of frame sections, not shown in FIGS. 1 and 2, spaced along the length of the tracks. One of said frame sections, however, is shown in FIG. 4 and identified generally by the reference numeral 36. Movement of the draw carriage along the tracks is effected by means of either a drive chain arrangement such as that shown in US. Patent No. 2,861,679, or by means of a hydraulic drive connected to the draw carriage through a sheave and cable arrangement. Since the specific drive system utilized forms no part of the present invention, it is deleted herefrom for purposes of simplicity.

The draw carriage 26 is provided with rigid side members 40 and 42 (FIG. 2) having keyways 44 and 46, respectively, machined in their forward ends. The keyways 44 and 46 receive cooperating keys formed in a gripper head 48 which carries three sets of gripping jaws 50 (FIGS. 1 and 4) which engage the forward reduced diameter ends of the tubes 1044. The gripping jaws 50 may be of the general type shown in the aforesaid US. Patent No. 2,861,679. Each set of jaws comprises a pair of grip bits 52, 54 (FIG. 4) carried in converging guideways in the gripper block 48, the arrangement being such that upon movement of the grip bits in one direction they will be caused to converge and grip a tube therebetween; while movement of the grip bits in the opposite direction will cause them to diverge and release the end of the tube. A suitable actuating mechanism for the grip bits 52 and 54 of each set of gripping jaws 50 includes a pneumatic cylinder 55 (FIGS. 1 and 2) having connected thereto a piston and plunger 56. The plunger 56, in turn, actuates a lever 58, pivotally mounted at 59, which engages the ends of the grip bits 52 and 54 such that upon movement of the plunger 56 to the right as viewed in FIG. 1, the 5p bits 52 and 54 will be caused to converge upon the reduced diameter end of an associated one of the tubes extending through one of the dies 16-20. Normally, spring means 61 are utilized for the purpose of urging the plunger 56 to the left as viewed in FIG. 1 whereby the grip bits 52 and 54 are maintained in a separated or diverged condition except during an actual drawing operation. In this respect, the cylinder 55 is normally single-acting with the grip bits 52 and 54 being caused to diverge initially by the forward thrust of the tube as it leaves its die, and thereafter maintained diverged by the spring means 61.

In the operation of the drawbench, the reduced diameter ends of the tubes, mounted on the aforesaid mandrels, are inserted through the dies 1620 and the draw carriage 26 moved to its extreme right-hand position shown in FIGS. 1 and 2 adjacent the die plate 22. At this time, the grip bits 52 and 54 are separated to receive the reduced diameter ends of the tubes 16-14. Just prior to the drawing operation, the single-acting pneumatic cylinders 55 are pressurized to cause, through plungers 56 and linkages S8, converging movement of the grip bits 52 and 54 of each set of jaws 50 whereby they will engage the forward ends of the tubes. Thereafter, the draw carriage 26 is caused to move away from the die plate 22 by means of the aforesaid drive chain or hydraulic cylinder arrangement, whereupon the tubes -14 are drawn through the dies. In this process, the diameters of the tubes are decreased while their lengths are increased.

At the completion of a drawing operation, the trailing ends of the tubes 10-14 will snap through the dies 16-20. Since, however, the tubes are not all of the same length as shown in FIG. 2, they do not leave their associated dies 16-20 at the same time. As mentioned above, the action of each tube in leaving its associated die is somewhat similar to that which occurs when one end of a taut elastic band is released. That is, the kinetic energy stored in the tube will cause it to jump forwardly; and in this process the grip bits 52 and 54 are caused to diverge and permit the tube to move forwardly under the draw carriage 26. In FIG. 1 it can be seen that the centerlines of the grip bits 52 and 54 are beneath the floor 60 of the draw carriage 26, whereby the tubes can jump forwardly without striking any part of the carriage.

If no means are provided for preventing the tubes from jolting forwardly, they could slam against the end of the bench and produce the dog-legged and tangled condition described above. Shock absorbers, deflectors and the like have previously been employed on the draw carriage for the purpose of dissipating the kinetic energy of the newlydrawn tubes; however these devices do not facilitate even stacking of the tubes with their trailing ends aligned and, more importantly, do not prevent dog-legging.

Therefore, in accordance with the present invention, upper and lower pinch roll assemblies 62 and 64, carried on pivoted arms 66 and 68, are employed to frictionally engage the tubes 10, 12 and 14 during a drawing operation. Only the lower roll assembly 64 is shown in FIG. 2, and it will be noted that the pivoted arms 68 are carried on a shaft 70 beneath the tracks 32 and 34. Extending between the arms 68 is a bar 72 having connected thereto the piston rod of a hydraulic or pneumatic cylinder 74 (FIG. 1) the arrangement being such that when the cylinder 74 is pressurized in one direction, the arms 68 and roll assembly 64 carried thereby will be elevated upwardly into engagement with the undersides of the tubes 10-14, whereas pressurization of the cylinder 74 in the opposite direction will lower the arms 68 and roll assembly 64. In a somewhat similar manner, the arms 66 for the upper roll assembly 64 are mounted for rotation on a shaft 67 and are connected through linkage 76 to the piston of a second hydraulic or pneumatic cylinder 78 whereby the roll assembly 62 may be elevated or lowered by appropriately pressurizing the cylinder 78.

The upper and lower roll assemblies 62 and 64 are substantially identical in construction, the lower assembly being shown in FIG. 5. It comprises three rolls 80A, 80B and 800, one for each of the tubes 10-14. Each roll 80A-80C comprises a first, stepped cylindrical member 86 having a reduced diameter portion which carries an annular rubber or neoprene element 88, this element being that which engages an associated one of the tubes 10-14. The element 88 is held in position by means of an annular member 90 threaded onto the end of the reduced diameter portion 86.

Each of the rolls 80A-80C is mounted for rotation on a non-rotatable shaft 92 carried between the arms 68 by means of antifriction ball bearings 94 and 96. As shown, the bearings and, hence, the rolls 80A-80C are spaced apart by means of spacer rings 98 surrounding the shaft 92. It will be noted that the shaft 92 is formed in two parts 93 and 95. One of such parts 93 is permanently connected to the left arm 68 shown in FIG. 5 and has an axial bore 100 in its right end which receives a reduced diameter portion 102 of the other part 95, this latter part being detachably carried on the arms 68 by means of 6 nuts 104 which facilitate disassembly of the mechanism. Behind the roll assembly 64 is an angle 106 (FIG. 6) carried between the arms 68. The angle 106, in turn, carries three generally M-shaped cores of magnetically permeable material 108A-108C, each of said cores having wound on two of its legs electromagnetic coils 110 and 112. Each of the cores 108A-108C is positioned directly opposite an associated one of the annular members 90. As shown in FIG. 6, each meber 90 has formed in its periphery a plurality of slots 114 in a manner similar to a motor armature. With the arrangement shown, the coils 110 and 112 on each core 108A-108C will produce lines of flux which pass through their associated members 90, the slots 114 providing surfaces which travel at substantially right angles to the direction of flux. Thus, when the coils 110 and 112 are energized, and assuming that the rolls A-80C are rotating, the magnetic lines of flux will create eddy currents within the elements to produce a braking or retarding effect.

It is essential that the rolls 80A-80C on the upper and lower roll assemblies 62 and 64 be mounted on antifriction bearings, such as ball bearings 94 and 96, to minimize the drag on-the tubes during the application of drawing force. That is, it is desirable to apply a drawing force just under the elastic limit of the metal of the tube to achieve maximum possible reduction in wall thickness during a single draw. Any drag created by the rolls could cause breakage of the tubes and, hence, the necessity for freely rotating rolls. The roll assemblies must be spaced ahead of the die plate 22 by an amount sufficient to permit the tubes to come to rest without having their ends pass through the rolls. In one actual embodiment of the invention, the preferable distance has been found to be about sixteen feet.

With refrence again to FIGS. 1 and 2 it will be noted that beneath each of the dies 16-20 is an associated light source 116 which produces a light beam passing through the axis of an associated one of the dies. Above each of the dies 16-20 and in the path of the beam of light from a cooperating one of the light sources 116 is a photocell 118. The light sources 116 are not positioned directly beneath each of the tubes .10-14 for the reason that if they were oil might drop onto the light source. With the arrangement shown, it will be appreciated that during a drawing operation and before the ends of tubes leave their associated dies, the light beams between the light sources 116 and photocells 118 are interrupted. When, however, the trailing end of atube snaps through the die, it will no longer interrupt the light beam which now shines on its photocell 118.

With specific reference now to FIG. 8, it can be seen that each photocell 118 is connected to an associated control circuit 120, 122 or 124. Each control circuit, in turn, is connected to the energizing coils and 112 on an associated one of the cores 108A-108C. With the arrangement shown, each photocell 118 will actuate its control circuit 120, 122 or 124 to deenergize the coils 110 and 112 when the light beam is blocked between the light source 116 and photocell 118. 'Thus, during the drawing operation and as the draw carriage initially moves away from the die plate 22, the coils 110 and 112 will be deenergized and the rolls 80A-80C on the lower roll assembly will rotate freely, as will those on the upper roll assembly. When, however, the trailing end of the shortest tube snaps through its associated die, the light beam between its light source 116 and photocell 118 will no longer be interrupted, whereupon the photocell will actuate the appropriate control circuit 120, 122 or 124 to energize a set of coils 110 and 112. This action, of course, produces lines of flux which pass through the annular member 90 for that roll to apply a retarding or braking force, thereby stopping the tube. With the arrangement shown, each tube is stopped independently of the others, the apparatus being operable regardless of whether one, two or three tubes are drawn on the bench.

It has been found that with the arrangement of braking rolls shown, the trailing ends of the tubes 14 will come to rest in substantial alignment.

In order to assist in depositing the tubes in a receiving bin 126 (FIG. 4) at the side of the drawbench in an untangled condition with their trailing ends aligned, a tilting table arrangement, generally indicated at 128, is provided. The arrangement 128 comprises a plurality of beams 130 pivotally mounted as at 132 on the spaced frame sections 36 disposed along the drawbench tracks 32 and 34. The beams 130 are disposed adjacent and parallel to inclined portions 131 of the farme sections 36. Extending between the spaced beams 130 is a plywood panel 134 adapted to be elevated into the susbtantially horizontal dotted-line position shown where it is directly beneath the tubes during a drawing operation. It will be appreciated, however, that the plywood panel 134 is interrupted at the location of the roll assemblies 62 and 64 such that the lower roll assembly 64 may pass upwardly through the panel 134 to engage the tubes during a drawing operation. The panel 134 communicates with a similar panel 136 at the lower end of the inclined portions 131 such that when the beams 130 are in the full-line positions shown in FIG. 4, a continuous inclined table is provided for the drawn tubes which roll from panel 134 onto panel 136 and thence into the receiving trough 126 where they may be picked by an overhead crane for a subsequent drawing operation.

During a drawing operation with the draw carriage 26 moving away from the die plate 22, the beams 130 are moved into the horizontal positions shown by the dotted lines in FIG. 4 with the panel 134 directly beneath the tubes. As the trailing end of each tube passes through its associated die, its kinetic energy will be dissipated by the inherent inertia of the rolls 80A-80C in the upper and lower roll assemblies 62 and 64, along with the retardation effect produced by the aforesaid electromagnetic braking means. After the end of the final tube snaps through its associated die and comes to rest, all of the tubes will be held between the roll assemblies 62 and 64 with their ends aligned, or substantially aligned. At

this time, the ends of the drawn tubes will rest on the panel 134, but a portion of the tubes will still be held between the roll assemblies 62 and 64. Thereafter, the cylinders 74 and 78 are pressurized to separate the roll assemblies 62 and 64 whereby the drawn tubes will lie flush on the panel 134. Finally, the beams 130' are rotated from their horizontal positions into the inclined position shown in full lines in FIG. 4 whereby the drawn tubes will roll from panel 134 onto panel 136 and into the receiving trough 126.

In order to actuate the tilting table assembly 1 28, the linkage mechanism shown in FIGS. 4 and 7 is provided. On each of the spaced frame sections 36 is a bracket 138 which supports a horizontally-extending shaft 140. Carried on each shaft 140 is a centrally pivoted toggle arm 142 having its lower end pivotally connected to an actuating rod 144 which interconnects all of the toggle arms 142. When the actuating rod 144 is pulled to the right as viewed in FIG. 7, all of the toggle arms 142 will rotate in a counterclockwise direction; whereas movement of the actuating rod 144 in the opposite direction will cause clockwise rotation of all of the toggle arms .142.

Connected to the upper end of each toggle arm 142, by means of a universal joint 146, is a linkage 148. The upper end of the linkage 148, in turn, is connected through a similar universal joint :150 to the right end of an associated one of the beams 130 as viewed in FIG. 4. When the actuating rod 144 is pulled to the right as viewed in FIG. 7, the beams 130 will be caused to rotate in a clockwise direction as viewed in FIG. 4 to move the platform 134 into the horizontal dotted-line position shown beneath the tubes being drawn. Movement of the actuating rod 144 in the opposite direction, however, will cause the beams 130 to rotate in a counterclockwise direction as viewed in FIG. 4 to move the platform 134 into its full-line inclined position where the drawn tubes may roll into the receiving trough 126.

Summarizing the operation of the drawbench arrangement of the invention, the draw carriage 26 is moved along the tracks 32 and 34 toward the die plate 22 while reduced diameter forward ends of the tubes -1014 are inserted through the dies 16 20. During this time, the cylinders 74 and 78 are pressurized to separate roll assemblies 66 and 68 and .permit passage of the draw carriage therebe-tween. As the draw carriage is returned to the dies, the actuating rod 144 is moved to the left as viewed in FIG. 7 to cause the beams 130 and the platform 134 carried thereby to assume a horizontal position parallel to the axes of dies 16-20. When the draw carriage 26 reaches the die plate 22, the cylinders 55 are actuated to cause the grip bits 52 and 54 of each set of jaws 50 to engage the forward ends of tubes v10 14, followed by movement of the draw carriage 26 away from the die plate 2 2. In this process, the tubes are drawn through the dies, but since the tubes interrupt the light beams between light sources 116 and photocell .1118, the coils 1 10 and 112 on cores 108A-108C are not energized and the rolls A80C on roll assemblies 62 and 64 rotate freely. Immediately after the draw carriage passes the roll assemblies 62 and 64, the cylinders 74 and 78 are pressurized to cause the roll assemblies 62 and 64 to move toward opposite sides of the tubes. The pressure on the roll assemblies effected by cylinders 74 and 78 is as great as possible without crushing the tubes, thereby assuring good frictional contact between the two. The rolls, however, freely rotate and apply very little drag because of the fact that the rolls 80A-80C are all mounted on ant-ifriction bearings.

When the trailing end of the shortest tube snaps through its associated die, the light beam between its corresponding light source 116 and photocell 118 will no longer be interrupted, whereupon the coils I and 112 for that particular tube will be energized to almost instantaneously apply a retarding force to the lower roll 80A, 80B or 80C. Of course, when the tube snaps free of its die, it will be released by the grip bits 52 and 54 and will jolt forwardly underneath the draw'carriage '26. The kinetic energy of the tube, however, is dissipated independently of the other tubes by the inherent inertia of the upper and lower rolls which frictionally engage it, along with the braking force applied by the electromagnetic retarding means.

As each tube snaps through its associated die, it will come to rest in the manner described above with its forward and trailing ends rest-ing on the platform 134. At this point, the cylinders '74 and 78 are pressurized to separate the roll assemblies 62 and 64, whereupon the drawn tubes will lie fiat or flush upon the platform 134 with their trailing ends substantially aligned. Finally, the actuating rod 144 is moved to the left as viewed in FIG. 7 to thereby tilt beams .130 and platform 134 to permit the drawn tubes to roll into the receiving trough 126 to produce a uniform and neat bundle in which the trailing ends of the tubes are aligned. At this point the draw carriage is returned to the die plate 22 and the cycle repeated.

In cases where relatively thick-walled tubing is being drawn and there is no danger of exceeding the elastic limit of the tubing, a constant braking force may be applied to one set of rolls 62. or 64. Such an arrangement is illustrated in FIGS. 9 and 10 showing a modified form of the lower roll assembly 64. The assembly includes three rolls 152A, 152B and 152C corresponding to rolls 80A-80C shown in FIG. 5. The rolls 152A-152C are mounted for free rotation on a common shaft 154, the shaft being carried on space-d arms 156 and 158 corresponding to arms 68 shown in FIG. 5.

Extending between the arms 156 and 158 and secured thereto is a plate 160 which carries three cylinder assem blies 162A, 162B and 162C. By reference to FIG. 10 it will be seen that each cylinder assembly 162A- 162C includes a fiber or the like shoe element 164 reciprocable within a bore 166, the cylinder assembly 162B for roll 152B being shown in FIG. 10. The shoe 164 is in frictional engagement with a smooth annular portion 167 of an associated one of the rolls 152B. Behind the shoe 164 in the bore -166 is a coil spring 168 provided with an adjustment scre'w assembly .170. With the arrangement shown, the force applied to the roll 152B by the shoe 164 can be adjusted by the screw assembly .170, thereby effecting a constant drag on the roll for the punpose of decelerating the tubes after they leave their associated dies. In this manner, the tubes will come to rest between the rolls at the completion of a simultaneous drawing operation with their ends substantially aligned.

As will be appreciated, the annular rubber or neoprene elements 88 shown in FIG. 5 will eventually wear and this wear occurs unevenly from roll-to-roll. Consequently, it is desirable in certain cases to provide means for adjusting each roll individually to compensate for wear of its annular neoprene or the like element. Such an arrangement is shown in FIGS. 11 and 12 and again includes three rolls 172A, 172B and 172C each provided with an annular neoprene or the like element 174 corresponding to elements 88 shown in FIG. 5. It will be assumed that the assembly shown in FIGS. 11 and 12 is a top roll assembly 62 and that the illustration in FIG. 11 is a bottom view of such an assembly. The assembly again includes side arms 176 and 178 pivotally mounted at 180 and connected through arm 182 (FIG. 12) to an actuating cylinder 184 corresponding to cylinder 78 shown in FIG. 1. Extending between the arms 176 and 178 are three plates 186, 187 and 188. Spaced along the plate 188 are bearing blocks 190A, 190B and 190C each of which carries for pivotal movement, a pair of arms 192 and 194. Extending between the forward ends of adjacent arms 192 and 194 is an axle 196 which carries an associated one of the rolls 172A-172C. Extending between the ends of each set of arms 192 and 194 opposite rolls 172A-172C is a pin 198 connected to a clevis 200. Secured to the clevis 200 is a threaded shank portion 202 which extends through an opening in the plate 186. A coil spring 204 surrounds the shank portion 202 between the plate 186 and a bolt 206, the arrangement being such that the spring 204 will tend to rotate the arms 192 and 194 about the central axis of bearing block 190A, 190B or 190C and into engagement with the plate 187. Upon downward movement of the roll assembly 62 toward the tubes being drawn, the rolls 172A- 172C will contact the tubes while the arms 192 and 194 for each roll rotate in a clockwise direction as viewed in FIG. 12 against the force of spring 204, the spring serving to securely seat the roll against the tube. With the arrangement illustrated, it will be appreciated that each roll is individually and automatically adjusted by the springs 204 so as to insure its snug engagement with an associated tube being drawn.

It is, of course, also desirable to have the center line between each set of rolls coincide with the longitudinal axis of the die. Otherwise, the tube will be flexed upwardly or downwardly by the rolls. This condition could occur, for example, due to uneven wear of the neoprene inserts in the upper and lower rolls. A system for insuring the correct spacing of the rolls is shown in FIG. 13 wherein elements corresponding to those shown in FIG. 1 are identified by like reference numerals. It will be noted that the arms 68 of the lower roll assembly 64 engage a stop member 208 which can be selectively positioned by means of an adjusting screw 210. The screw 210 is adjusted periodically to insure that when the arm 68 is in abutment with the stop member 208, the center of rotation of the rolls on the lower roll assembly 64 will be spaced from the axis of the dies by an amount equal to the radii of the rolls. In order to insure that the upper roll assembly 62 will not push the lower roll assembly 64 downwardly and thereby create a condition of misalignment, the cylinders 74 and 78 are connected to a control valve 216 through pressure regulators 212 and 214, respectively. The valve 216, of course, serves to selectively connect one end of each cylinder 74 and 78 to a pump 218 while connecting the other end to a reservoir 220. When it is desired to cause the roll assemblies 62 and 64 to converge, the control valve 216 is adjusted to connect the pump 218 through pressure regulators 212 and 214 to the lower ends of cylinders 74 and 78; while the upper ends of the cylinders are connected through the control valve 216 to a reservoir 220. The pressure regulators 212 and 214 are adjusted such that a greater pressure is applied to the lower cylinder '74 than the upper cylinder 78, thereby insuring that the arms 68 of the lower roll assembly 64 will be in abutment with the stop member 208 to establish the proper spacing between the rolls such that the tubes being drawn will 'not be deflected from the longitudinal center lines of the dies.

Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit require ments without departing from the spirit and scope of the invention.

We claim as our invention:

1. In a drawbench of the type including a plurality of drawing dies, a track structure extending parallel to the axes of said dies on one side thereof, and a draw carriage movable along said track structure for pulling workpieces through the dies; the combination of means for dissipating the kinetic energy of newly-drawn workpieces as they snap through the dies at the completion of a drawing operation, comprising pairs of individual rolls for each of said workpieces, each of said pairs of individual rolls being arranged to frictionally engage opposite sides of an associated one of said workpieces after the draw carriage leaves the dies during a drawing operation, each pair of rolls being rotatable independently of the other pairs, an electromagnetic braking means inductively coupled to the rolls for applying a retarding braking force to at least one roll in each pair when their associated workpiece snaps free of its die.

2. The combination of claim 1 and including an annular portion on said one roller in each pair formed from magnetically permeable material, axially-extending slots in the periphery of said annular portion, a core of magnetically permeable material in close proximity to said annular portion, and electrical winding means on said core arranged to produce lines of flux which pass through the core and cut through the projections on the periphcry of said annular portion formed by said slots.

3. In a drawbench of the type including a plurality of drawing dies, a track structure extending parallel to the axes of said dies on one side thereof, and a draw carriage movable along said track structure for pulling workpieces through the dies; the combination of means for dissipating the kinetic energy of newly-drawn workpieces as they snap through the dies at the completion of a drawing operation, comprising pairs of individual rolls for each of said workpieces, each of said pairs of individual rolls being arranged to frictionally engage opposite sides of an associated one of said workpieces after the draw carriage leaves the dies during a drawing operation, each pair of rolls being rotatable independently of the other pairs, electromagnetic braking means for applying a retarding braking force to at least one roll in each pair when their associated workpiece snaps free of its die, means indi vidual to each workpiece for sensing passage of the trailing end of that workpiece through its associated die and adapted to produce an electrical signal when it senses passage of the trailing end through the die, and circuit means responsive to said electrical signal for actuating said electromagnetic braking means to apply a retarding force to said rolls.

4. The combination of claim 3 wherein said means individual to each workpiece for sensing passage of the trailing end of a workpiece through its associated die includes a photocell and a source of light adapted to produce a light beam which is directed against said photocell but which is interrupted by a tube during a drawing operation and prior to passage of the trailing end of that tube through its associated die.

5. In a drawbench of the type including a drawing die, a track structure extending parallel to the axis of said die on one side thereof, and a draw carriage movable along said track structure for pulling workpieces through the die, the combination of means for dissipating the kinetic energy of a newly-drawn workpiece as it snaps through the die at the completion of a drawing operation, comprising a pair of rolls arranged to frictionally engage opposite sides of said workpiece after the draw carriage leaves the die during a drawing operation, said rolls being normally freely rotatable, and electromagnetic braking means inductively coupled to the rolls and actuable when the trailing end of a workpiece leaves the die for applying a braking force to said rolls to retard rotation of the same.

6. The combination of claim 5 wherein said electromagnetic braking means includes an annular magnetically permeable member on at least one of said rolls, and electromagnetic coil means adapted to produce lines of flux which cut through said annular magnetically permeable member on said one roll.

7. In a drawbench of the type including a plurality of drawing dies, a track structure extending parallel to the axes of said dies on one side thereof, and a draw carriage movable along said track structure for simultaneously pulling workpieces through the dies; the improvement of means for preventing damage to the workpieces by virtue of their being propelled forwardly as their trailing ends leaves the dies, the said means comprising workpieceengaging means for said workpieces, said workpieceengaging means being arranged to frictionally engage opposite sides of each individual workpiece during a drawing operation, means for moving said workpieceengaging means toward and away from the workpieces, and separate pressure adjustment means associated with each separate workpiece for individually regulating the pressure exerted by the workpiece-engaging means on an associated workpiece when the workpiece-engaging means is in frictional engagement therewith.

8. In a drawbench of the type including a plurality of drawing di'es, a track structure extending parallel to the axes of said dies on one side thereof, and a draw carriage movable along said track structure for simultaneously pulling workpieces through the dies; the improvement of means for preventing damage to the workpieces by virtue of their being propelled forwardly as their trailing ends leave the dies, the said means comprising a separate pair of workpiece-engaging members for each individual workpiece, said members being arranged to frictionally engage opposite sides of said individual workpiece during a drawing operation, separate arm means for each separate pair of workpiece-engaging members, means for moving said arm means and the workpiece-engaging members carried thereby toward and away from the workpieces, and separate adjustment means associated with each separate arm means for individually regulating the pressure exerted by each pair of members on its associated workpiece when the arm means is moved toward the workpieces and the members are in frictional engagement therewith.

9. The improvement of claim 8 wherein each separate arm means includes a first arm movable toward and away from an associated one of said workpieces, a second arm pivotally mounted on said first arm about an axis extending perpendicular to said individual workpiece, one of said members being carried on said second arm, and variable pressure means for urging said second arm to rotate about its pivotal connection to the first arm so as to force said member into frictional engagement with said associated workpiece.

References Cited by the Examiner UNITED STATES PATENTS 2,262,432 11/1941 Rodder 205-3 3,175,385 3/1965 Mitchell 72281 3,210,983 10/1965 Wells 72291 CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner. 

1. IN A DRAWBENCH OF THE TYPE INCLUDING A PLURALITY OF DRAWING DIES, A TRACK STRUCTURE EXTENDING PARALLEL TO THE AXES OF SAID DIES ON ONE SIDE THEREOF, AND A DRAW CARRIAGE MOVABLE ALONG SAID TRACK STRUCTURE FOR PULLING WORKPIECES THROUGH THE DIES; THE COMBINATION OF MEANS FOR DISSIPATING THE KINETIC ENERGY OF NEWLY-DRAWN WORKPIECES AS THEY SNAP THROUGH THE DIES AT THE COMPLETION OF A DRAWING OPPERATION, COMPRISING PAIRS OF INDIVIDUAL ROLLS FOR EACH OF SAID WORKPIECES, EACH OF SAID PAIRS OF INDIVIDUAL ROLLS BEING ARRANGED TO FRICTIONALLY ENGAGE OPPOSITE SIDES OF AN ASSOCIATED ONE OF SAID WORKPIECES AFTER THE DRAW CARRIAGE LEAVES THE DIES DURING A DRAWING OPERATION, EACH PAIR OF ROLLS BEING ROTATABLE INDEPENDENTLY OF THE OTHER PAIRS, AN ELECTROMAGNETIC BRAKING MEANS INDUCTIVELY COUPLED TO THE ROLLS FOR APPLYING A RETARDING BRAKING FORCE TO AT LEAST ONE ROLL IN EACH PAIR WHEN THEIR ASSOCIATED WORKPIECE SNAPS FREE OF ITS DIE. 